Toggle lever system



Marqh 23, 1965 H. HECHT 3,174,347

TOGGLE LEVER SYSTEM Filed May 15, 1961 5 Sheets-Sheet l INVE/V TOR ELM/UT HEC'HT A TTORNEY March 23, 1965 H. HECHT 3,174,347

TOGGLE LEVER SYSTEM Filed May 15, 1961 5 Sheets-Sheet 2 INVENTOI?" HELMUT HEC'HT y} 5 N VEN 70/? H. HECHT TOGGLE LEVER SYSTEM SSheets-Sheet 3 HE'LlV/UT HECHT A TTORNEYS March 23, 1965 Filed May 15, 1961 Fig. 13

March 23, 1965 H. HECHT 3,174,347

TOGGLE LEVER SYSTEM Filed May 15, 1961 5 Sheets-Sheet 4 INVENTUA HELMUT HECHT ,qrromvsys March 23, 1965 H, HECHT 3,174,347

TOGGLE LEVER SYSTEM Filed May 15, 1961 5 Sheets-Sheet 5 INVENTOR HEL MUT HECHT A T TOENE Y5 United States Patent C) p 3,174,347 H A j TGGGLE LEVER SYSTEM Helmut Hecht, Goppingen, Germany, assignor to May- Pressenbau Ltd., Schwabisch Gmund, Germany Filed May 15, 1961, Ser. No. 199,907 1 Claim. (Cl. 7438) The invention relates to a toggle lever system.

Toggle lever presses with a short toggle lever articulated on a stationary pivot and with a long toggle lever articulated to the latter at the knee joint and guided reotilinearlyat its other end, both these toggle levers ineluding an acute angle with one another, and the knee joint being movable by means of a crank drive are already known. Such toggle lever presses are usually de signed for a predetermined stroke of the free end of the long toggle lever denoted the hinge point, but it has been found in practice that it would be convenient to have the length of stroke adjustable. Moreover it is necessary to adapt the toggle lever presses as regards the number of their down strokes to the actual working conditions, and for this reason toggle lever presses are being built having variable lengths of stroke and variable number of strokes for the various kinds of work to be performed by these presses.

The invention has the 'object of adjusting the length of strokes and also the number of strokes per minute by simple manipulations on the press without changing its drive.

With this and other objects in view, which will become apparent later from this specification and the accompanying drawings, I provide a toggle lever system comprising in combination: a stationary pivot, a short toggle lever articulated on said pivot, a long toggle lever, a knee joint articulating said short and long toggle levers to one another, the said two toggle levers including an acute angle with one another, or rectilinear guide guiding the free end of the' said long toggle lever, a crank drive in driving connection with the said knee joint, and adjustment means operatively connected to the said stationary pivot and capable of adjusting the same between one end position in which the lines of action of the said short and long toggle levers never come into a position of mutual coincidence and another end position in which the same move beyond the said position of mutual co-incidence.

By such an adjustment on the one hand the length of stroke may be varied within wide limits, and on the other hand the number of strokes may be doubled.

In some cases it is sutficient when the stationary pivot is merely adjustable to several predetermined positions of a peculiar kind, since for the kind of processes to be carried out with the toggle lever system concerned some preferred adjustments suflice. In some cases it may even be sutficient when only two predetermined positions of the stationary pivot are available, namely a first position resulting in a single working stroke for each revolution of the crank, and a second position resulting in two working strokes per revolution of the crank.

Moreover, in some toggle lever systems a preferred position exists in which a single maximum length working stroke per revolution of the crank is performed, and this happens when the lines of action of the two toggle levers mutually coincide once only at every revolution of the crank.

The adjustment of the stationary pivot may be effected, as stated hereinabove, in such a manner that the number of strokes is doubled, and there are a great many positions of the stationary pivot, at which any two consecutive strokes are of diiferent length. The length of stroke may however be made equal for all strokes only by one suitable adjustment of the stationary pivot, and this is.

the case, when the two lines of action of the toggle levers "ice mutually coincide once only at every revolution of the crank and when the knee joint at each revolution of the crank oscillates equal angles on both sides of the position of mutual coincidence.

The adjustment of the stationary pivot may be eifeoted in any manner desired, in as much as it is by no means necessary to adjust the stationary pivot perpendicular to the movement of the hinge point. In many cases a different kind of adjustment is even preferable. A simple construction results, when the stationary pivot point or pivot pin is mounted on an eccentric shaft or eccentric disc, and this shaft or disc "is mounted rotat-ably. By turning the shaft or eccentric disc, various positions of the stationary pivot may then be adjusted. Preferably the'turning of the eccentric disc is effected by externally accessible means, for example a worm gearing being provided for this purpose.

In order to fix the adjustment of the eccentric in predetermined positions, a detent device may be provided, for example in that a detent pawl may engage into rccesses of the eccentric, a safety means for the detent pawl being preferably provided in addition.

In many cases two parallel toggle lever systems are provided at a certain distance from one another which act on a common presser member, for example on a press punch, on both sides of which they are arranged. In this case the adjustment of the stationary pivots of both toggle lever systems must be carried out in unison, and this is attained conveniently in that the stationary pivots and/or associated eccentrics are fixedly connected 10 one another. For example the two eccentrics may be coupled form-closed to one another, and when the stationary pivots and/or their adjustment members are arranged immovable relative to one another, both stationary pivots may be adjusted in unison, if desired by adjusting one stationary pivot only.

The adjustment of the stationary pivot is explained in more detail with reference to diagrammatic illustrations, and an embodiment of the invention is illustrated by way of example in the accompanying drawings, in which:

FIGS. 1 and 2 show a toggle lever system with the stationary pivot in the normal position in which a single working stroke, but not the maximum stroke is performed per revolution of the crank.

FIGS. 3 and 4 show a toggle lever system with the stationary pivot in a position in which one maximum stroke is performed per revolution of the crank.

FIGS. 5 to 9 show a toggle lever system in a position in which two working strokes of unequal length are performed per revolution of the crank.

FIGS. 10 to 12 show a toggle lever system in a position in which two equal working strokes are performed per revolution of the crank.

- FIG. 13 is a front elevation of a toggle lever press, wherein two toggle lever systems are provided, the stationary pivots of which are adjustable in accordance with the invention.

FIG. 14 is a side elevation to FIG. 13 with one side plate omitted.

FIG. 15 is a part-section of FIG. 13 on a larger scale, with the toggle lever system omitted.

FIG. 16 is a section on the line 16-16 of FIG. 15.

FIG. 17 is a section on the line 1717 of FIG. 16.

In all the diagrammatic illustrations of the toggle lever system to be described in what follows identical reference characters are used for identical parts.

In the diagrammatic arrangement of a toggle lever syste-m according to FIGS. 1 and 2 a long toggle lever denoted 10 and a short toggle lever denoted 11 are articulated to one another at a knee joint 12. The end of the long toggle lever 10 averted from the knee joint, denoted as the hinge point 13, is guided rectilinearly in a a guide 14. The end of the short toggle lever averted from the knee joint 12 is articulated to a stationary pivot 15.

To the knee joint a connecting rod 16 is articulated which is also articulated to a crank pin 17 of a crank disc 18 set in rotation by means not shown.

Upon rotation of the crank disc 18 the knee joint 12 is reciprocated by the connecting rod 16 in the usual way, and in the position of the stationary pivot according to FIGS. 1 and 2 and denoted I, the two toggle levers and 11 come not into mutual coincidence. A stroke of the magnitude a results at each revolution of the crank.

In the position II of the stationary joint according to FIGS. 3 and 4 the toggle levers 10 and 11 are in mutual coincidence once at every revolution of the crank (conf. particularly FIG. 4), and a maximum stroke b results once at each revolution of the crank. The former position I of the stationary pivot is indicated in chaindotted lines in FIG. 4.

In the illustration of FIGS. 5 to 9 the stationary pivot 15 is in a position III, and in FIG. 5 the former positions I and II are indicated in chain-dotted lines. As follows from FIGS. 5 to 9, the toggle levers 10 move beyond the position of coincidence, and accordingly there results two strokes c and d per revolution of the crank, which are of diiferent magnitude. The relative magnitude of these strokes may be varied by adjustment of the stationary pivot, and in the example of FIGS. 10 to 12 the stationary pivot is in a position IV in which the two strokes e per revolution of the crank are equal. In FIG. 10 likewise the former positions of the stationary pivot are indicated.

In FIGS. 13 to 17 a structural embodiment is illustrated by way of example which corresponds to the diagrams according to FIGS. 3 and 4 and 10 to 12.

A press frame is denoted 20 in general, and side plates 21 and 22 are attached laterally toit. A press punch is denoted 23, and a press table 24-.

In the bottom portion of the press the usual drive mechanism is accommodated, which does not form part of the invention and is accordingly not illustrated in detail. The gearing for the driving of the press has an input pinion 28 in mesh with a gear wheel 29, which is in turn rigidly connected to a shaft 30 on which two crank discs 31 are fixed. The crank discs have each a crank pin 32, on which a connecting rod 33 is articulated with one end. The other ends of these connecting rods are articulated each to a knee joint pin 35, on which moreover a short toggle lever 38 and a. long toggle lever 39 are pivotally mounted. The end of the long toggle lever is connected at 40 to the press punch 23, and at 41 a guide slot is provided for the guidance of the end of the long toggle lever. These parts of the toggle lever system are known and have accordingly not been described in more detail.

On the whole two toggle lever systems of the kind described hereinabove are arranged on both sides of the press punch, and each short toggle lever 38 is articulated to an eccentric pin 45 of an eccentric disc 46, which is rotatably mounted on the frame 20 of the press. The ececntric discs 46 each have an inwardly projecting extension 47 and 48, respectively, at the inner ends of each of which a square head 49 is arranged. A coupling sleeve 50 is pushed over these two square heads, so that the latter and accordingly the eccentric discs and eccentric pins cannot move relative to one another.

In order to arrange the eccentric pins accurately alike one may proceed in such a manner that the entire section consisting of two eccentric discs, the extensions and the square heads is produced in one piece, and after the machining of the central square portion the latter is severed in the middle.

Over the coupling sleeve 50 a turnbuckle 51 is pushed which is screwed on to a left hand thread 53 of one extension 47, and on a right hand thread 54 of the other extension 48. By the aid of a tool (not shown in detail in the drawings) to be inserted into an insertion hole 57 the turnbuckle 52 may be turned, which involves the clamping or loosening, respectively, of the eccentric discs 46. The extension of the upper eccentric disc in FIG. 16 has a Worm wheel toothing 60 in mesh with a worm 61, and after loosening the turnbuckle the two eccentric pins 45 and consequently the stationary pivots of the two toggle lever systems can be adjusted by turning this worm. After the adjustment the two eccentric discs are then firmly drawn towards one another by the aid of the turnbuckle, and thus arrested in their position. Although the detention of the eccentric discs and accordingly of the stationary pivots described hereinabove would suffice in many cases, it is convenient to provide in addition a means for locking the eccentric discs in certain positions. For this purpose for each of the eccentric discs a safety pawl 66 is pivotally mounted at 65 and biased by a spring 67 towards the associated eccentric disc. In the eccentric disc a number of rest recesses are provided, in the present case two rest recesses 69 and 70, into which the locking pawl may engage in order thus to lock the eccentric discs in two pre-determined positions. The locking pawls are each held by a safety screw 72 in the locking position. The pivoting of the locking pawls 66 may be effected, after loosening the safety screw against the bias of the spring 67 by turning a square head 74 actually accessible from outside.

While I have described herein and illustrated in the accompanying drawings what may be considered a typical and particularly useful embodiment of my said invention, I wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated; for obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent, is:

A toggle-lever press, comprising a frame, a tool carrier reciprocably sliding in said frame in an operating direction, first and second links connected with a knee joint, each of said links having spaced from said knee joint an auxiliary hinge point which together with said knee joint forms a line of action, said auxiliary hinge point of said first link adjusting the latter relative to said tool carrier, a rotor journaled in said frame for rotation about an axis extending at right angles to said operating direction, said rotor comprising a cylindrical part provided with arresting slots, the latter extending parallel to said axis, said rotor further comprising an end face, joint means fixed on said end face eccentrically to said axis and connecting said auxiliary hinge point of said second link with said rotor, a locking dog for said rotor pivoted on said frame to be brought in engagement with one of said arresting slots to arrest said rotor in an operating position, screw means operable to engage said locking dog to force the latter into one of said slots, driving means to operate said knee joint by cycles, each cycle consisting in a movement of said knee joint to and fro between two end positions and across an intermediate position, in which latter position said lines of action of said links are in mutual coincidence, said end positions being symmetrically spaced with respect to said intermediate position, and said driving means having a crank pin eccentrically pivotable around an axis spaced from said rotor and a connecting rod connecting said crank pin with said knee joint.

References Cited by the Examiner UNITED STATES PATENTS 2,054,428 9/36 Klocke -281 X 2,600,242 6/52 May 108231 2,851,888 9/58 Scholin 74-38 2,857,768 10/58 Rall 74-40 2,942,484 6/ 60 Diff 7440 BROUGHTON G. DURHAM, Primary Examiner. 

